1. Technical Field
The present invention relates to a planographic printing plate precursor.
2. Background Art
Planographic printing is a method of printing using plate material having ink-receiving lipophilic regions and ink-repellent regions (hydrophilic regions) that do not receive ink but receive dampening water. Photosensitive planographic printing plate precursors (PS plates) are currently widely used. In practice, for such PS plates, PS plates are widely used that include a support, such as an aluminum plate, and a photosensitive layer provided on the support. Such PS plates are exposed imagewise and developed, thereby removing the photosensitive layer in non-image portions, and printing is performed utilizing the hydrophilicity of the substrate surface and the lipophilicity of the photosensitive layer in image portions. Highly hydrophilic properties are required of the substrate surface in order to prevent the non-image portions from being stained.
Conventionally, anodized aluminum substrates, or anodized aluminum substrates which have been subjected to silicate treatment in order to further increase the hydrophilicity thereof, have been typically used as the hydrophilic substrate or as the hydrophilic layer employed in planographic printing plates. Much research into hydrophilic substrates and hydrophilic layers employing such aluminum supports has been carried out. Techniques that use polymers are known where a substrate is processed with an undercoating agent including polyvinylphosphonic acid, or a polymer having a sulfonic acid group is used as an undercoat layer below a photosensitive layer. In addition, there are also proposals for the use of polyvinylbenzoic acid or the like as an undercoating agent.
Further, there are proposals regarding hydrophilic layers where a flexible support such as PET (polyethylene terephthalate) or cellulose acetate is used rather than a metal support such as aluminum. For example: Japanese Patent Application Laid-Open (JP-A) No. 8-272087 discloses a technique in which a hydrophilic layer including a polymer, which is cured with hydrolyzed tetraalkyl orthosilicate, is provided on a PET support; JP-A No. 8-292558 discloses a technique of providing a hydrophilic layer which has a phase separation structure having two phases, including a phase with a hydrophilic polymer as a main component and a phase with a hydrophobic polymer as a main component; and JP-A No. 7-1853 discloses a hydrophilic layer including a copolymer of vinylphosphonic acid and acrylamide provided on an aluminum support. In addition, there are techniques proposed which use polyvinylbenzoic acid or the like as an undercoating agent.
Such hydrophilic layers exhibit better hydrophilic properties than those conventionally used, thereby providing planographic printing plates with which prints with no stains can be obtained when printing is initiated. However, there is the problem that such layers tend to peel off during the course of repeated printing and their hydrophilic properties tend to deteriorate over time. There is thus a demand for planographic printing plate precursors with which many prints can be obtained with no staining, and without causing the hydrophilic layer to peel from the support and without deterioration in the surface hydrophilic properties, even under more severe printing conditions. There is also a demand for further improved hydrophilicity and improved printing durability by the adhesiveness between image portions and a support (hydrophilic layer), from a practical perspective.